1. Field of the Invention
The present invention relates to a medical prosthesis for human implantation, and in particular, to an artificial device for repairing neurons, such as a biological nerve guide.
2. Description of the Prior Art
Nerve tissues have regenerating power, and even the central nervous system has been discovered in recent years to possess regenerating power. However, nerve tissues are fragile and the regeneration speed is slow so that when neurons are damaged, natural regeneration and repair often are unable to reconnect the nerve because of the slow growth rate. Also, the repair path is often blocked by the faster growing surrounding regenerated tissues or scar tissue.
To address these problems, some scientists have tried to utilize a guide to connect the two ends of a defective nerve to prevent the path from being blocked, and this guide is called a nerve guide. Some conventional nerve guides are prepared from non-degradable materials so that irritation from foreign matter was always present while regeneration of nerve tissues was also adversely affected. Some of these conventional nerve guides are prepared from degradable materials such as polylactic acid or polyglycolic acid, but their degraded products exhibit localized acidity, adversely affecting the growth, the proliferation and the migration of nerve cells.
Other conventional nerve guides are produced from natural materials such as animal blood vessels, but conventional glutaraldehyde is utilized in the treatment process, resulting long-term residual toxicity and rather potent cellular toxicity while also adversely affecting the growth and proliferation of nerve cells. One of the serious drawbacks of the current nerve guides is the thick guide wall which does not allow the penetration of nutrients and the passage of blood supply, and the nerve cells inside the guide cannot obtain enough nutrients for desirable differentiation and migration to repair damaged tissue.
Another conventional nerve guide is produced from degradable natural materials such as animal collagen, but the mechanical properties such as flexibility, toughness, and kink resistance are not desirable. A noticeable drawback is that the degradation speed is difficult to match with the speed of nerve tissue regeneration, so that the treatment result is often uncertain.